This application claims the priority of German patent document 198 31 514.7, filed Jul. 14, 1998 and PCT International Application No. PCT/EP99/04670, filed Jul. 6, 1999, the disclosures of which is expressly incorporated by reference herein.
The invention relates to a method and apparatus for controlling an infinitely variable change speed gear of a motor vehicle, including provision for manual action of a selector level by the vehicle operator.
In known infinitely variable automatic change speed gears for a motor vehicle, a change of the transmission can take place infinitely, and without shifting points along the entire driving range. The transmission is usually set automatically as a function of vehicle operating condition, such that the engine can, as a rule, be operated in proximity to its operating point which is optimal with respect to the effect. Such infinitely variable automatic change speed gears relieve the driver, and can achieve a higher overall efficiency than conventional change speed gears, although they have a lower mechanical efficiency because the engine always runs in the proximity of the operating point which is optimal with respect to the effect. In addition, the spread is usually larger and the number of possible gears is unlimited in the case of infinitely variable automatic change speed gears.
German Patent Document DE-AS 12 24 580 discloses an infinitely adjustable V-belt change speed gear in which the adjustment of the V-belt (and thus the adjustment of the transmission) is to take place by means of a lever which can be secured against a displacement.
In European Patent Document EP 0 217 221 A2, a method is discloses for controlling a CVT change speed gear and an auxiliary change speed gear. The CVT change speed gear and the auxiliary change speed gear are connected in series, and the shifting points of the auxiliary change speed gear are defined by means of stored shifting patterns. The shifting pattern that is used is selected via the selector lever.
German Patent Document DE 41 20 540 and European Patent Document EP 676 564 disclose methods and devices for controlling an infinitely variable change speed gear, having a control unit that has a first operating mode in which the gear of a change speed gear is set automatically as a function of signals of a selector device and operating variables of the vehicle. In addition, there is also a second operating mode in which a stepped change speed gear, which can be influenced directly by the driver, is simulated. The shifting steps or the number and spread of the change speed gears can be optimized according to the vehicle handling. These control arrangements, however, do not take into account the specific advantages of infinitely variable change speed gears. The latter change speed gears are treated as automatic quasi step gears.
German Patent Document DE 196 09 585 A1 discloses a method and apparatus for controlling an infinitely variable change speed to gear in which the adjustment of an arbitrary gear can be carried gout in a quasi infinitely variable manner. However, the method of actuating the operating element decides whether a significant or only a slightly larger or smaller gear is set. Thus, the change of the gear can be stopped by the adjusting path of the selector lever, the force acting upon it or its adjusting speed. A dependence can also be established on how long the selector lever or the operating element is held in its deflecting position. Thus, arbitrary smaller or larger gear jumps can occur when the transmission is adjusted.
One object of the invention is to provide a control method and apparatus for an infinitely variable change speed gear, in which an appropriate gear within the overall gear range of the change speed gear can be explicitly selected manually for each driving situation, or for each driving intention, taking into account the specific advantages of infinitely variable change speed gears.
This and other objects and advantages are achieved by the transmission control method and apparatus according to the invention, in which a selector device comprising an operating element that can be actuated in at least two directions is connected with a control unit, and emits to it a signal generated corresponding to an actuation. The control method has at least one operating mode in which the operator of the vehicle can influence directly the speed-increasing ratio by manual actuation of the selector device. That is, the speed-increasing ratio is changed directly corresponding to the control command of the vehicle operator.
According to a feature of the invention, when the selector device is actuated in one direction, the change first takes place by a minimum adjustment of the speed-increasing ratio toward a higher gear. When the selector device is actuated continuously, a continuous adjustment subsequently takes place in the direction of a higher gear. On the other hand, when the selector device is actuated in the other direction, the speed-increasing ratio is first set by a minimum adjustment toward a lower gear and, when the selector device is continuously actuated in this direction, a continuous adjustment takes place in the direction of a lower gear, specifically as long as the selector device is actuated.
In one embodiment of the invention, at the start of an actuation of the selector device in one direction, the speed-increasing ratio is adjusted continuously at a first defined adjusting speed in the direction toward a higher gear. If the actuation of the selector device is interrupted before a given time period has been reached, the speed-increasing ratio is adjusted to a predetermined value at a second adjusting speed greater than the first given adjusting speed. In this case, for example, the minimum adjustment can be carried out. If the selector is actuated for a period which lasts beyond the given time period, the continuous adjustment takes place in the direction of a higher gear at a third given adjusting speed until the actuation is interrupted. The third given adjusting speed is lower than the second but not the first adjusting speed; that is, it may also be equal to the first adjusting speed. An analogous process takes place when the selector device is actuated in the other direction.
According to another embodiment of the invention, in the case of a so-called tip command (brief actuation of the selector device in one direction), a minimum adjustment always takes place which corresponds to approximately one gear jump in a stepped shifting system. When the stepped shifting system has a conventional design, this minimum adjustment results in one rotational engine speed jump (for example, to approximately 1,500 r.p.m.). As required, a fast-reaction change of the rotational speed can be achieved in this case. However, the desire for a smaller rotational speed change (for example, between 0 and 1,500 r.p.m.) cannot be achieved. In another embodiment, therefore, a predefined adjustment in the sense of a gear jump takes place only after the detection of a short tip command (actuation time of the selector device in a direction below a given time period).
The adjusting speed during the continuous transmission change can preferably be a function of the actuation duration or the actuating pressure. This has the advantage that, when the adjustments are smaller, good proportioning is possible; at the same time, when the adjusting operations are larger, an excessive waiting period is unnecessary.
It is particularly advantageous for a special function to be implemented in one or both possible actuation directions of the operating element of the selector device, such that an automatic driving program or an automatic driving strategy becomes active when the selector device is actuated beyond the required extent. This can be accomplished, for example, by two successive tip commands within a predefined time window or an overpressing of a resistor, similar to a kick-down actuation. When the selector lever is actuated correspondingly in the direction of a higher gear, for example, an automatic driving strategy may be activated which aims at a no-compromise maximal economyxe2x80x94driving in the range of the minimum consumption.
Resumption of normal manual driving operation (that is, to the basic function) can take place by a brief actuation of the selector device in the opposite direction. In this case, the transmission selected by the preceding automatic program would preferably be maintained.
When the selector device is correspondingly actuated in the direction toward a lower gear, a driving program could be selected as a special automatic driving strategy that permits a maximal driving performance; that is, the speed-increasing ratio is in each case selected such that the respective maximal engine power is available for each throttle valve angle. In this case, comfort aspects can be taken into account, particularly with a view to frequent transmission changes with rapidly changing throttle valves. Also in the case of this driving program, normal manual driving operation can be resumed by actuating the selector device in the opposite direction.
In a special embodiment of the invention, it is possible to equip the selector device with a selector lever as the operating element, which can be moved back and forth in a manual shifting channel. In addition to this manual shifting channel, a parallel automatic shifting channel can preferably be provided, the automatic shifting channel and the manual shifting channel being connected with one another by a transverse shifting channel. In the automatic shifting channel, conventional selector lever positions, such as P (parking position), R (reverse driving position), N (neutral position) and D (normal driving position) can be provided. In the driving position D, an automatically controlled, normal driving operation would then be carried out. During the transition from one shifting channel into another, the respective other driving program could then be activated.
As an alternative, the selector device can also be a tip switch or two push button switches which are preferably arranged in the steering wheel. The change speed gear transmission changes can then be carried out by a corresponding actuating of the selector switches, without the driver""s having to remove his hands from the steering wheel.